I felt NT was an apt comparison because not only is it the basis for the current Windows, it also was their first 32-bit offering, i.e. where stuff got serious. 16-bit Windows was a fairly different beast. 9x was certainly influential but (1) is now dead and (2) came after NT, borrowed lots from NT in the beginning. In light of this, drawing comparisons between 1.0 and Win8 doesn't seem all that appropriate to me.
I guess my hesitation was caused by the assumption that while windows before NT was all 16 bit / 32 bit hybrid; it's API's are still essentially the same which is what you would care about when re-platting an API.
However I will concede my argument like a true gentlemen, as I now realize the ABI is what we should care about. It is almost certainly different even if the API's haven't fluxed that much, and that is what a re-platt project would most care about.
My point was the legacy is there and it's pretty large, should not be understated. Apple may not care so much about compatibility between releases or with NeXT binaries from 1987 (though I don't think Windows code from '87 works so well on NT either), but the old code is there and if your argument is that sort of thing doesn't help binary compatibility, then that's a problem. I was making my point in shorthand fashion, so I didn't even touch on Mach which is very old as well.
People have this impression that OS X is flashy and new and immune to or not experienced in code rot, and I didn't think it rings all that true.
